Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/50—Multilayers
  • B05D7/52—Two layers
  • B05D7/53—Base coat plus clear coat type
  • B05D7/532—Base coat plus clear coat type the two layers being cured or baked together, i.e. wet on wet
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/08—Processes
  • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/30—Low-molecular-weight compounds
  • C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
  • C08G18/3225—Polyamines
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/30—Low-molecular-weight compounds
  • C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
  • C08G18/3271—Hydroxyamines
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/30—Low-molecular-weight compounds
  • C08G18/38—Low-molecular-weight compounds having heteroatoms other than oxygen
  • C08G18/3819—Low-molecular-weight compounds having heteroatoms other than oxygen having nitrogen
  • C08G18/3821—Carboxylic acids; Esters thereof with monohydroxyl compounds

Definitions

• the invention relates to coating compositions which are particularly suitable for the preparation of the basecoat for two-coat coatings of the basecoat/clearcoat type, and which comprise organic diluents, at least one resin containing urethane and urea groups, and, where appropriate, other resins, pigments and other conventional additives in common use.
• Basecoat/clearcoat coatings are prepared by first applying a pigmented basecoat which, after a brief flush-off period, is overcoated by a clearcoat without a baking stage (wet-on-wet process), the basecoat and clearcoat being subsequently baked together.
• the coating compositions for the preparation of these basecoats must be capable of being processed by the expedient wet-on-wet process, in general use today, i.e. they must be capable, after an as short a drying time as possible without a baking stage, of being overcoated with a transparent topcoat, without the appearance of any defects due to solvent action of one coat on the other and of any "strike-in" phenomena.
• a basecoat for metallic finishes capable of being processed by the wet-on-wet process, must therefore produce paint films in which the metallic pigments are present after the application in a suitable spatial orientation and in which this orientation becomes rapidly set in such a way that it cannot be disturbed in the course of further painting processes.
• EP-A-137,256 discloses coating compositions for the preparation of the basecoat for two-coating coatings of the basecoat/clearcoat type which contain polyurethane elastomers and/or polyurea elastomers as binder components.
• the object of the present invention was to make available coating compositions for the preparation of the basecoat for two-coat coatings of the basecoat/clearcoat type which would be free from the shortcomings referred to above.
• compositions according to the main concept of the principal claim which comprise at least one resin containing urethane and urea groups, which resin is obtainable by reacting
• a prepolymer (A) containing isocyanate groups by subsequently reacting the isocyanate groups of the prepolymer (A), at least in part, with p1 a3) an adduct produced from a (meth)acrylic ester, preferably an acrylic ester, and an aliphatic or cycloaliphatic compound containing at least two aminic hydrogen atoms, the adduct containing at least one active aminic hydrogen atom.
• the benefits achieved by the invention consist essentially in the absence of any color differences between the original finish and the refinish when the coating compositions according to the invention are used.
• a further important benefit is that the resins containing urethane and urea groups, used in the basecoat compositions according to the invention, may be prepared by using an a3) component containing hydroxyl groups and then converted to satisfactory basecoats even without the addition of polyol components. It is furthermore possible to incorporate in the resin molecule hard polyester segments without producing incompatibility phenomena when aminoplast resins are added.
• the coating compositions according to the invention also possess the advantages of the coating compositions disclosed in EP-A-137,256.
• the resins containing urethane and urea groups, contained in the coating compositions according to the invention, are obtainable by reacting
• any diol which is suitable for the preparation of polyurethane paint resins may in principle be used as the component a1). These diols may be low-molecular, but diols with a higher molecular weight may also be used. Examples of low-molecular diols are ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, butane diol, neopentyl glycol and hexane-1,6-diol.
• diols with a higher molecular weight examples include polyether diols and polyester diols.
• Suitable polyether diols are poly(oxyalkylene) diols such as, for example, poly(oxytetramethylene) glycol, poly(oxyethylene) glycol, poly(oxypropylene) glycol etc.
• Polyester diols are preferably used as the component a1). These polyester diols are obtainable by esterifying organic dicarboxylic acids or their anhydrides with organic diols. Diols which are customarily used for the preparation of these polyesters, comprise alkylene glycols such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, and neopentyl glycol, as well as other glycols, such as hydrogenated bisphenol-A, cyclohexanedimethanol, caprolactone diol (for example the reaction product of ⁇ -caprolactone and ethylene glycol), hydroxyalkylated bisphenols, polyether glycols, for example poly(oxytetramethylene)glycol and the like. Other diols may, however, also be used.
• alkylene glycols such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, and neopenty
• the acid component of the polyester diols usually consists of dicarboxylic acids or their anhydrides having 2 to 18 carbons atoms per molecule.
• suitable acids are phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, glutaric acid, hexachloroheptenedicarboxylic acid, tetrachlorophthalic acid and other dicarboxylic acids of various types.
• the corresponding anhydrides may of course also be used in place of the acids.
• polyester diols which contain isphthalic acid as the acid component and have an average molecular weight (number average) of 400 to 2,000, are particularly preferred as the component a1).
• di-isocyanates There are many such di-isocyanates.
• suitable di-isocyanates are 1,4-tetramethylenedi-isocyanate, hexamethylenedi-isocyanate, 2,2,4-trimethylhexane-1,6-di-isocyanate, isophoronedi-isocyanate, bis(isocyanatocyclohexyl)methane and methyl-cyclohexyldi-isocyanate.
• Adducts produced from (meth)acrylic esters and aliphatic and/or cycloaliphatic compounds containing at least two aminic hydrogen atoms are used as the component a3). These adducts must contain at least one aminic hydrogen atom reactive toward isocyanate groups (a so-called active aminic hydrogen atom). The number of the active aminic hydrogen atoms must be selected so that no crosslinked resins are obtained. Adducts with 1 to 3 active aminic hydrogen atoms are in general used as the component a3). Adducts with two active aminic hydrogen atoms are preferably used.
• the preparation of the adducts employed as the component a3) is carried out in a simple manner by reacting an aliphatic and/or cycloaliphatic compound containing at least two aminic hydrogen atoms, with (meth)acrylic esters.
• the addition reaction may be preformed in the molten state or in solution at temperatures between 20° and 120° C., preferably below 50° C. The reaction is in the majority of cases exothermic.
• the adducts used as the component a3) are advantagously prepared by dissolving the compound containing at least two aminic hydrogen atoms in a suitable solvent and gradually adding the (meth)acrylic ester with stirring at such a rate that the reaction temperature does not exceed 50° C.
• Methacrylic esters as well as acrylic esters may be used for the preparation of the component a3).
• Acrylic esters are preferably used.
• suitable (meth)acrylic esters are ethyl(meth)acryliate, methyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate and 2-ethylhexyl(meth)acrylate.
• (Meth)acrylate esters containing hydroxyl groups are preferably used.
• alkyl(meth)acrylates containing hydroxyl groups are 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate as well as in particular a reaction product of one mol of a hydroxyalkyl (meth)acrylate, preferably a hydroxyalkyl acrylate, particularly hydroxyethyl acrylate, with 1 to 3, preferably 2 mol of ⁇ -caprolactone.
• the component a3) is prepared by reacting the (meth)acrylate esters described above with a compound containing at least two aminic hydrogen atoms.
• a compound containing at least two aminic hydrogen atoms To this purpose the reaction conditions and the type and amount of the compound containing at least two aminic hydrogen atoms must be so selected that the resultant adduct contains at least one, preferably 1 to 3 active aminic hydrogen atoms.
• Suitable compounds containing at least two aminic hydrogen atoms are, for example, ethylenediamine, 1,2- or 1,3-propylenediamine, 1,6-hexanediamine, 2-methyl-1,6-hexanediamine, 1-methyl-2,4-diaminocyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 1,3- or 1,4-bisaminomethyl-cyclohexane or 4,4'-diaminodicyclohexylmethane.
• Compounds which contain primary amino groups are preferred.
• the resin containing urethane and urea groups, contained in the coating compositions according to the invention, is advantageously prepared by first reacting the components a1) and a2) to form a prepolymer (A) containing isocyanate groups.
• This reaction may be carried out by wellknown methods of polyurethane chemistry.
• the reaction between the components a1) and a2) is preferably carried out in an inert organic solvent (for example toluene, xylene, ethyl acetate or butyl acetate).
• the amounts of the components a1) and a2) chosen for the reaction are preferably such that the molar ratio of a1) to a2) is 0.5:1.0 to 0.9:1.0.
• the adduct a3) is prepared in a separate reaction vessel in the manner described above.
• the final preparation of the resin according to the invention may be then carried out by a slow addition of the prepolymer (A) to the adduct a3).
• the proportion of the amount of prepolymer (A) to that of the component a3) is preferably so chosen that 1 to 2 active aminic hydrogen atoms are present per one isocyanate group.
• a coating composition which is suitable as a basecoat composition for basecoat/clearcoat coatings may be prepared from the resin containing urethane and urea groups according to the invention, described above, by generally known methods.
• the coating compositions according to the invention contain in addition to the resin according to the invention customary organic diluents, other resins where appropriate, pigments and other conventional additives in common use.
• the organic diluents contained in the coating compositions according to the invention can consist of volatile organic liquids or mixtures of liquids, normally employed in coating compositions as polymer solvents or polymer dispersants.
• aliphatic hydrocarbons for example hexane and heptane
• aromatic hydrocarbons such as, for example, toluene and xylene
• petroleum fractions with various ranges of boiling points which are mainly aliphatic but may also comprise a substantial aromatic content
• esters for example butyl acetate, ethylene glycol diacetate and 2-ethoxyethyl acetate
• ketones for example acetone and methyl isobutyl ketone
• alcohols for example butyl alcohol.
• polyesters which may be contained in the coating compositions according to the invention in addition to the resin according to the invention, are polyesters described in EP-A-137,256.
• the coating compositions according to the invention advantageously contain a crosslinking agent.
• Suitable crosslinking agents are, for example, aminoplast resins, phenolic resins or blocked polyisocyanates.
• Aminoplast resins such as condensation products of formaldehyde with melamine, urea or benzoguanamine, are preferred. These aminoplast resins frequently contain methylol groups or similar alkylol groups which are preferably at least partly etherified with an alcohol.
• the coating compositions according to the invention preferably contain 40 to 80% by weight, particularly preferably 55 to 65% by weight, based on the binder solids, of the resin according to the invention containing urethane and urea groups.
• the coating compositions according to the invention may contain any pigment which is suitable for a basecoat/clearcoat coating.
• Coating compositions which contain metal platelet pigments, preferably aluminum platelets, either individually or in admixture, are particularly preferred.
• the preferred coating compositions may contain further colorant non-metallic pigments.
• the coating compositions according to the invention may also contain further customary additives such as fillers, plasticizers, stabilizers, wetting agents, dispersants, flow-out agents, antifoams and catalysts either individually or in admixture in the customary amounts.
• further customary additives such as fillers, plasticizers, stabilizers, wetting agents, dispersants, flow-out agents, antifoams and catalysts either individually or in admixture in the customary amounts.
• crosslinked polymeric microparticles and/or a copolymer prepared from 85 to 95% by weight of ethylene and 15 to 5% by weight of vinyl acetate may be added to the coating compositions according to the invention.
• Suitable polymeric microparticles are for example those described in EP 29,637 A2.
• the invention further relates to a process for the preparation of a multicoat protective and/or decorative coating on a substrate surface in which
• a coating composition which comprises organic diluents, at least one resin containing urethane and urea groups, pigments and, where appropriate, other resins and other conventional additives in common use, is applied as basecoat composition,
• the basecoat composition comprises at least one resin containing urethane and urea groups, the resin being obtainable by reacting
• a coating composition as described above, is applied as basecoat composition.
• the resultant basecoat is overcoated by a transparent topcoat composition without a baking stage (wet-on-wet process).
• the basecoat and topcoat are finally baked together.
• topcoat compositions any known non-pigmented or only transparently pigmented coating compositions are suitable as topcoat compositions. These may be conventional solvent-containing clearcoats, water-dilutable clearcoats or powder clearcoats.
• Pretreated metal substrates are particularly suitable as the substrates to be coated, but non-pretreated metals and any other substrates, such as, for example, wood and plastics, may be coated by a basecoat/clearcoat coating by the process according to the invention.
• the invention also relates to a substrate which has been coated by the process described above.
• the invention also relates to resins containing urethane and urea groups which are obtainable by reacting
• 1682 g of 2,2-dimethylpropane-1,3-diol, 472 g of adipic acid, 479 g of phthalicanhydride and 1074 g of isophthalic acid are weighed into a 6-liter four-necked flask provided with a stirrer, a thermometer, a packed column having a thermometer at its head, a distillation bridge, a descending condenser and a condensate receiver.
• the reaction mixture is first heated to 160° C. with stirring. After water has begun to split off, the temperature is so controlled that the temperature at the head of the column does not exceed 100° C. Esterification is continued at a temperature of 230° C. max., until the acid value is 5.
• the resultant polyester has a hydroxyl value of 118.
• the polyester is dissolved in butyl acetate to give an 80% solution.
• the viscosity of the resultant mixture is adjusted to 24 seconds (ISO 4) (spraying viscosity) with a mixture of 50 parts of butyl acetate, 25 parts of butylglycol acetate and 25 parts of n-butanol.
• the solids content of the basecoat compositions is 20% by weight.
• Example K2 of EP-A-137,256 has been taken over except that instead of the melamine resin, 163 g of a hexamethylene di-isocyanate trimerized via the biuret groups, marketed by Bayer AG under the trade name DESMODUR N, has been used.
• the solids content is 49.5%.
• This 2-component clearcoat has only a limited shelflife and should be used up soon after preparation.
• the measurement of the brightness viewed directly and viewed obliquely is carried out against a calibrated reference.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Paints Or Removers (AREA)
• Laminated Bodies (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=6333007

Family Applications (1)

Country Status (10)

Cited By (8)

Families Citing this family (5)

Citations (4)

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• 1987
  • 1987-08-04 DE DE3725784A patent/DE3725784A1/de not_active Withdrawn
• 1988
  • 1988-07-19 WO PCT/EP1988/000650 patent/WO1989001004A1/fr not_active Application Discontinuation
  • 1988-07-19 ES ES198888111599T patent/ES2035180T3/es not_active Expired - Lifetime
  • 1988-07-19 US US06/445,610 patent/US5169922A/en not_active Expired - Fee Related
  • 1988-07-19 DE DE8888111599T patent/DE3875420D1/de not_active Expired - Lifetime
  • 1988-07-19 EP EP88905834A patent/EP0377570A1/fr active Pending
  • 1988-07-19 AT AT88111599T patent/ATE81661T1/de not_active IP Right Cessation
  • 1988-07-19 EP EP88111599A patent/EP0302296B1/fr not_active Expired - Lifetime
  • 1988-07-19 JP JP63505874A patent/JPH06102769B2/ja not_active Expired - Lifetime
  • 1988-07-19 BR BR888807639A patent/BR8807639A/pt not_active IP Right Cessation
  • 1988-07-21 ZA ZA885292A patent/ZA885292B/xx unknown
  • 1988-08-03 CA CA000573675A patent/CA1334038C/fr not_active Expired - Fee Related

Patent Citations (4)

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